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17-39

amplitude of fluctuation of the luminous flux (of a source run on alternating current)

relative amplitude of the periodic fluctuation of the luminous flux as measured by the ratio of the difference between the maximum and the minimum instantaneous luminous flux, Φmax and Φmin respectively, to the sum of both of these values:

Unit: 1

NOTE 1 This ratio is usually expressed in % and is then known under the expression "percent flicker" which, however, should be deprecated.

NOTE 2 Another means sometimes used by the lighting industry to characterize the fluctuation in light output is "flicker index", which is defined by the ratio of 2 areas deduced from the diagram representing the variation of the instantaneous flux over a period of time; the area of the diagram above the average value is divided by the total area under the curve (this total area is the product of the average value and the given period of time).